This application is a divisional application of U.S. patent application Ser. No. 13/605,298, filed on Sep. 6, 2012, the disclosures of which are incorporated in their entirety by reference herein.
1. Field of the Invention
The invention disclosed and claimed in this application relates to the treatment of oil and/or gas wells. One example of such treatment is commonly referred to as fracturing the formulation around an oil or gas well. Fluid with certain chemical additives and a proppant are injected into the formation surrounding either a vertical or horizontal well to form cracks or passageways in the formation to stimulate the production of the well.
2. Description of Related Art
Currently there are several techniques utilized to stimulate producing of a well by fracing. Typically a packer or plug is utilized to isolate a particular portion of the well and the fracing fluid is injected into the isolated portion under high pressure. Once a given portion of the well is treated in this manner, a second zone uphole of the first zone is isolated by a second packer or plug that cuts off flow to the downhole portion of the well that has been treated.
U.S. Pat. No. 7,322,417 discloses a plurality of vertically spaced production layers 1 and a plurality of valves 14. A ball is captured on a valve seat 94 which will cause an increase in pressure to open valve 14. This allows fracturing fluids to enter the annular region that surrounds the valve. The balls may be formed of a dissolvable or frangible material, which allows the ball to be dissolved or eroded to open up communication upstream through the casing.
U.S. Pat. No. 7,134,505 discloses a similar system in which a plurality of spaced apart packers 20 a-n and a plurality of valve bodies 26 c-n that capture balls of varying diameters to selectively open ports 16 c-e to allow fracturing fluids to flow into the isolated zones.
Stage frac methods include the use of pump down bridge plugs, perforating guns, and sliding sleeves. The current pump down method requires a drill out phase after frac with coiled tubing or jointed pipe. This is an expensive and time consuming process which involves additional risk of the coil tubing getting stuck in the wellbore. This time and operational risk is a significant impact item on the overall economics of oil and gas projects.
Sliding sleeves require that their exact position needs to be known as the casing is run into the well. The number of frac initiation points is limited and the cost is significant for each sleeve. Sleeves may malfunction either during opening or closing. Higher risk comes from incomplete frac distribution and limited reservoir drainage.